krusher was never that high...he got a point reset to 1000 when he was ~3900. Since map rank just looks at game logs, it wouldn't be able to tell that his points were reset, so it continued to think he was at 3900 when he was at 1000. So when he started playing again and went from 1000 to 2500, map rank tacked those 1500 points onto his old high score, putting him at the 5.5k you have listed there. He never crossed 4k.